Wireless transmissions are typically packetized and transmitted as a series of related blocks, termed frames of data during available transmission windows. These frames of data are received at a receiver and are reassembled to form a coherent data stream. A problem exists in wireless systems in that sometimes a frame of data is transmitted at a transmitter but is never received or is corrupted before receipt at the receiver. To overcome this shortcoming, wireless systems typically have a system for the transmitter to determine that a given frame of data is received by the receiver. For example, in the IEEE 802.11 wireless standard, a transmitter after transmitting a frame awaits receipt of an acknowledgement transmission from the receiver to determine that the frame was successfully received by the receiver. In a case wherein an acknowledgement is not received for a given frame within a given amount of time, the transmitter will retransmit the frame during a next available transmission window. The retransmission may occur several times for a given frame when an acknowledgement indicating receipt of the given frame is not received by the transmitter. After some given number of transmission attempts, the transmitter will eventually discard the unsuccessfully transmitted frame and will no longer attempt retransmission. For certain types of data transmissions, such as a transmission of program instructions, loss of even a single frame of data may have an effect of rendering even successfully transmitted frames useless. Even in a case wherein the entire transmission is not rendered useless when a frame is lost, such as for voice transmissions, loss of voice frames reduces the perceived quality of the overall transmission and therefore is undesirable.
To increase the likelihood of a successful transmission, some transmitters have two or more transmitting antennas. However, wireless transmitters that have two or more transmitting antennas oftentimes still have trouble transmitting successfully on any one of the transmitting antennas. Systems exist that try to determine which antenna has a greater likelihood of transmitting successfully and then utilize this antenna for a given frame transmission. However, the conditions that determine which antenna is better for transmission may change rapidly and repeatedly, even within a span of microseconds. When a given frame is repeatedly retransmitted over a wrong antenna (e.g., an antenna that can not transmit successfully to a given receiver), the given frame may be eventually discarded. Accordingly, determining a most appropriate antenna for transmission may not always be sufficient.
It is an object of the present system to overcome disadvantages and/or make improvements in the prior art.